Re: Re: Aggregations etc.

Hello Franck,

I see your point about SQueryGeneric.  How about SQuerySelect, because it lets you explicitly specify a select list?  

I realize that you are busy but it would be good to at least do just the rename plus comment as soon as possible.  (I won't do it because it will break your code.)

I am a little concerned about getting too clever in SDriver about portability.  Supporting this type of thing for multiple databases is very hard.   I think that I would prefer that you just do this at the application layer.  You just have little methods that provide the right query for different DBs.  Could just return strings, or possibly SQuerySelect (given an SQuerySelect parameter).  I prefer strings, it is simpler.

Regards,

Anthony

At 04:49 PM 19/04/2009, you wrote:
>Hello Anthony,
>
>I've not be changing anything recently, except adding a rawInnerJoin
>method to SQuery, that truly adds an arbitrary table to a query (a table
>that has no explicit SFieldReference to the query).
>
>But I have also found I would need rawSelect(), so it is definitely a
>good idea :-)
>
>The point is we are also releasing a new version of our flgship product
>by the end of the month, so I'll be quite busy right until then...
>
>Just a few more comments:
>
>> I think that specifically SQueryAggregate and friends should be renamed into something like SQueryGeneric.  That is because the thing that is special about it is that it returns SRecordGenerics rather than SRecordInstances.  One use of SQueryGeneric is to do aggregates, but it is more general than that.
>
>Yes, but then, when SRecordInstance will extend SRecordGeneric, SQuery
>will also return SRecordGeneric... So, are we going to have an abstract
>SQueryGeneric, with SQuery and SAggregateQuery extending it, or do you
>think both should be merged in the long term ? (right now I wouldn't say
>so, but I'm not sure)
>> 
>> Thus we should also add the easy 
>>   .rawSelect(String rawSqlExpression, Object[]... parameters) 
>> which adds an arbitrary an arbitrary expression, plus .rawClause for completeness.
>
>Yes, that would be interesting...
>Another thing I found I'm missing is doing arbitray calculation and then
>doing an aggregate on it, but rawSelect wouldn't solve my problem
>altogether, as calculation might include database functions that are not
>standard.
>Typical example is I want to make a sum of durations for my records,
>grouped by whatever. Duration is defined by the difference between two
>timestamps... and this is something that in not standard in sql. So
>having portable code is not easy.
>
>eg. select sum( extract(epoch from endts) - extract(epoch from begints))
>will work for postgresql, but not for oracle etc.
>
>So another idea I had was to be able to augment SDriver (and
>SQueryGeneric) with specific functions (like duration(ts1, ts1)) that
>could be used in queries to allow to generate sql that will work in each
>database... I didn't do anything for now, as I'm not sure about the
>right way to do this (just add the functions I need, or think about a
>more clever pluggable functions system, ...)
>
>> 
>> The simple unification of SRecordInstance with SRecordGeneric would complete the process, but that can be done later.  I might make time do it myself because it will not affect your code.  (It is easy, just have SRecordInstance implement map, with 
>> 
>Fine.
>As I said, I won't have much time for the next two or hree weeks, but it
>should be better after that.
>
>Best regards,
>Franck

Dr Anthony Berglas, [email protected]       Mobile: +61 4 4838 8874
Just because it is possible to push twigs along the ground with ones nose
does not necessarily mean that is the best way to collect firewood.



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